Method and Configuration for Storing and Playing Back TV Transmissions

ABSTRACT

A method and a configuration for storing and playing back TV transmissions, in particular an improved method and configuration for operating a network PVR, include a PVR server for receiving digitally encoded TV channels. Terminals select TV transmissions to be stored and transmit the selection to the PVR server. The PVR server records the TV transmissions to be stored, wherein a small part of data items to be stored during recording is transmitted to the memory of the selecting terminal and a main part of the data items to be stored is recorded in a mass storage device coupled to the PVR server. The parts of the recording stored in the memory of the selecting terminal and in the mass storage device are combined in such a way that they can be played back through the use of the selecting terminal, either by the selecting terminal or by the PVR server.

The present invention relates to a method and a configuration for storing and playing back TV transmissions. In particular, the present invention provides an improved method and an improved configuration for operating a network PVR.

After tape-based analog video recording devices have for decades represented the only possible way for home users of recording and conveniently preserving transmissions broadcast by way of antenna, cable or satellite television, since fast and at the same time inexpensive video processors and powerful video codecs such as MPEG2 (1994) and MPEG4 (1998) have become available there has existed for several years a series of largely hard-disk based digital devices which offer a series of convenience functions alongside pure video recording.

This new generation of devices is often referred to as personal video recorder (PVR), sometimes also as digital video recorder (DVR). While these modern devices can naturally also be used as classic devices for the simple recording and subsequent playback of transmissions, their capabilities extend far beyond that level. A frequently used feature of a PVR is for example so-called time-shifted television, in which the user actually begins to play back a transmission while the recording is still running. Thanks to the powerful hardware of a modern PVR, the picture quality achieved in this situation is better than that of a conventional VHS or SVHS tape device.

Time-shifted television also enables the user to “pause” a transmission viewed live initially, to take a telephone call perhaps, and to continue the playback later, whereby it would appear to the user as if he had actually paused the live broadcast and continued it later. In the background, however, the user pressing the “Pause” button has caused his PVR to record the running transmission, and pressing the “Pause” button again results in the recorded transmission on the one hand continuing to be recorded and on the other already being played back.

The capability of a PVR which allows the user to skip large sections in a recording with minimum delay also enjoys great popularity. This is frequently used during playback to skip blocks of advertising contained in the recording. A series of services has established itself around this capability which facilitate the location of the limits of the advertising blocks, for instance by storing the beginning and the end of an advertising block as points in time relative to the beginning of a transmission as an index for the recording and thus enabling the advertising to be skipped automatically during the playback.

In addition to specially adapted consumer electronics devices, multimedia PCs with suitable software (known as home theater PC, HTPC) are also increasingly being used as PVRs. Technically, there is little difference between a special PVR and a PCPVR; both have a large (hard-disk) storage facility, adequate processor power and suitable video codecs.

Thanks to configurable software or firmware, both platform variants are in a position to offer the user further functions, such as searching for transmissions which fit thematically with his favorite transmissions. Common to both platform variants is the fact that the recording takes place locally with respect to the user and the quantity of transmissions that can be recorded is limited by the local disk storage unit. It is therefore often possible to transfer recorded transmissions from the internal memory of the device onto writable media such as (re-)writable CDs or DVDs. There is some effort involved in this however and, not least, the price of a PVR is also considerable. Furthermore, PVRs also suffer from the problem that a plurality of PVRs are additionally required in order to allow parallel recording of multiple transmissions. Expensive multituner devices only solve this problem to a limited extent because it will always be the case that fewer tuners are present than TV stations and moreover that the hardware of the PVR—sufficiently powerful for one channel—is reaching its limits with regard to the parallel recording of multiple channels.

In order to be able to offer users all the advantages of a PVR without them needing to invest in a PVR, a network PVR was proposed in the white paper “Network PVR: Everything an Demand”, Jay Schiller, nCube Corporation, available on the Internet at http://www.ncube.com/pressroom/downloads/nvpr-whitepaper.pdf, in which memory, coding logic and codecs are made available by a provider on the cable network. The user receives a device which allows him to select transmissions to store and to retrieve stored transmissions which are then transferred by means of a wideband connection in real time to the user. When compared with a PVR or an HTPC, such a device can be considerably less powerful. At the same time, the user can lease storage space practically without limit on the central PVR server while the operator of the PVR server only needs to provide one copy of each transmission which is then distributed when required to those users who have placed this transmission in their (virtual) memory.

In a development, such a network PVR can be implemented such that “programming” of the network PVR by the user is not required and the user instead has access to all the transmissions in his program assortment from approximately the most recent 4 weeks.

A problem in this situation however is the fact that only one copy of a transmission is stored for all users and either access to it by the users is possible for a certain time without restrictions or a database is used to keep a record of which user has “recorded” a particular transmission and access to the recording is then permitted or denied by the database. In certain legal systems this can lead to insoluble conflicts with rights owners of the broadcast transmissions and also with television providers and their terms of use.

An object of the invention is therefore to set down a method and a configuration for storing and playing back TV transmissions, which avoids this disadvantage.

This object is achieved by a configuration for storing and playing back TV transmissions, which comprises the following:

-   a PVR server with means for receiving a plurality of digitally coded     TV channels and means for feeding a plurality of terminals; -   at least one terminal with means for selecting TV transmissions to     be stored and means for transferring the selection to the PVR     server;

whereby the following are additionally provided:

-   in the PVR server, means for recording TV transmissions to be     stored, whereby a small part of the data to be stored with regard to     the recording is sent to a memory in the selecting terminal (local     part) and a main part of the data to be stored is stored in a mass     storage device coupled to the PVR server (central part); and -   means for combining the parts of the recording stored in the memory     of the selecting terminal and the parts stored in the mass storage     device coupled to the PVR server for playback by means of the     selecting terminal (combination of the local and central data).

The invention also relates to a method for storing and playing back TV transmissions, comprising the following steps:

-   reception of a plurality of digitally coded TV channels by a PVR     server which feeds a plurality of terminals; -   selection of TV transmissions to be stored by a terminal and     transfer of the selection to the PVR server; -   recording of TV transmissions to be stored, whereby a small part of     the data to be stored with regard to the recording is sent to a     memory in the selecting terminal and a main part of the data to be     stored is stored in a mass storage device coupled to the PVR server;     and -   combination of the parts of the recording stored in the memory of     the selecting terminal and the parts stored in the mass storage     device coupled to the PVR server for playback by means of the     selecting terminal.

Said problem is advantageously solved by the invention in that it is not the complete transmission which is stored in the network PVR but only the main (central) part and small (local) part of the data is stored in the terminal. The (central) data stored in the network PVR is thus no longer a complete transmission and thus no longer a useable transmission.

An advantageous embodiment makes appropriate provision whereby the main (central) part of the data to be stored which is stored in the mass storage device delivers decodable picture and sound information only when combined with the (local) data stored in the memory of the selecting terminal. This also ensures that only users who had also programmed the stored transmissions for recording are able to retrieve them because the terminal portion of the data required for the decoding is also stored only in the terminals of this user.

The small data set to be stored in the terminal makes it possible to dispense with conventional high-capacity hard disk drives in the terminal and to provide a flash memory or a mini hard drive as the terminal memory, a commercially available Hitachi Microdrive for instance. In this situation, it is possible to permanently couple the terminal data to a particular terminal by means of digital rights management in order to prevent users from exchanging this data amongst one another. It is thus possible to prevent users who had not programmed the stored transmission for recording from also seeing it. Alternatively, precisely this exchange process (with restricted scope) can be permitted for users in order to grant users the same rights when using the network PVR as when using analog tape devices where it is possible to pass on recordings without any difficulty.

In the terminal, for example header information, a time-limited starting sequence, or every n-th data packet of the video data to be stored can be stored; the remaining data to be stored is stored in the mass storage device coupled to the PVR server. In this situation, the data can for example be chosen such that a short intro can be played from the data present in the terminal in order to enable the user to decide immediately to delete the recorded transmission without combining the data beforehand. Or the data packets can be chosen such that a sequence of still images is present in the terminal.

The combination of the parts of the recording stored in the memory of the selecting terminal and the parts stored in the mass storage device coupled to the PVR server can take place in the PVR server, whereby the complete video data is then sent to the terminal as a realtime data stream for playback. This permits the construction of a particularly simple terminal with minimal computing power.

Alternatively, the combination of the parts of the recording stored in the memory of the selecting terminal and the parts stored in the mass storage device coupled to the PVR server can take place in real time in the terminal, whereby the incomplete video data is sent from the mass storage device coupled to the PVR server as a near-realtime data stream to the terminal, where it is supplemented by the data stored in the terminal and played back.

Preferred embodiments of the present invention will be described in detail in the following with reference to a drawing.

The single FIGURE shows a configuration 100 with a network PVR or PVR server 102 and terminals 104A . . . 104N fed by the latter. The PVR server 102 receives digitally coded TV channels from an encoder 120. The encoder in turn receives the TV channels from a receiver 122 which receives suitable TV signals by way of a terrestrial antenna 124 and/or satellite antenna 126 and/or TV cable 128. In this situation, the encoder 120 and the receiver 122 can be constructed as one device. The encoder 120 utilizes a codec such as MPEG2 or MPEG4 for example or codecs derived from these in order to convey the TV signals which are initially present in analog form into an efficient digital data format. If a TV channel is already available as a digital data stream, for example as a digital video broadcast DVB (received terrestrially as DVB-T, via cable as DVB-C or via satellite as DVB-S), the encoder 120 can forward this data stream unmodified to the PVR server 102 or modify it before forwarding, for example by matching the bandwidth of the data stream to the bandwidth of the link to the terminals 104.

The PVR server is coupled to a mass storage device 108, for example to a hard disk drive array (HDD array). Numerous methods are known in the art for building redundant mass storage device arrays from hard disks, which are nevertheless still able to deliver the stored data in its entirety in the event of failure of individual hard disks. The use of such a redundant array, for example a redundant array comprising independent hard disks (RAID), is advantageous in conjunction with the present invention because a PVR server 102 and the attached mass storage device 108 stores the major part of the TV recordings of numerous users.

The user terminals 104 are connected to the PVR server 102 for example by way of the TV cable network or a DSL link. Modern codecs permit an acceptable video quality with transfer rates upwards of a few hundred kbit/s. With the bandwidths of several Mbit/s that are technically possible over DSL links, two or more parallel video streams (for different playback devices in the user's household) or a single high-quality video stream are conceivable.

The terminals 104 are equipped with or coupled to local memory 110 which for example can be implemented as conventional hard disk or HDD 111 and/or as flash memory 112 and/or as RAM 113. Special forms such as mini hard drives available in flash memory card format are naturally also conceivable. In this situation, flash memory 112 has the advantage that storage of data is possible independent of the presence of a supply voltage and at the same time particularly quiet terminals 104 are made possible because flash memory has no rotating or other mechanical parts.

In this situation, the memory 110 can be permanently coupled to the terminal 104 or can be configured as exchangeable. Lesser demands apply to the memory 110 of the terminals 104 than to the mass storage device 108 in respect of redundancy and failsafe behavior. Provision can be made as a convenience feature for the user which enables him to produce backup copies of the parts of the recordings stored in his memory, for instance on a data medium (writable CD or DVD, external hard disk) not permanently situated in the terminal 104, using a network connection on a PC or also in a separate storage area offered by the PVR service provider (not shown).

With regard to the terminal or CPE 104, this can be a set-top box which is connected to a picture playback device 116. Alternatively, the terminal 104 can be integrated into the picture playback device 116. The picture playback device 116 can be a conventional television. Alternatively, it can also be a monitor which does not itself have a TV tuner. The terminal 104 has a user interface 106 which the user can use for example in order to select TV transmissions for recording or to manage his archive of recorded TV transmissions. This user interface can, as is normal in the realm of set-top boxes, be implemented such that the user makes inputs using a remote control and sees outputs displayed on the picture playback device 116.

When the user has selected a TV transmission, a data record identifying a TV transmission to be recorded is sent to the network-based PVR 102 which uses a scheduler to make the TV transmission available for recording. A user database—not shown—manages the transmissions allotted for recording by a user and checks the user's authorizations, for instance as to whether the user has subscribed to the corresponding TV channel.

When a TV transmission is broadcast the PVR server 102 checks whether a user (a single user is sufficient) has allotted this transmission for recording. If this is the case, the recording is carried out by dividing the data into a local and a central part and storing it accordingly in the memory 110 of the terminal 104 or in the mass storage device 108. In this situation, advantageously the main part of the data is stored centrally in the mass storage device 108 and the remaining data is sent to the local memory 110 of the requesting terminal 104. If the transmission has been programmed for recording on a plurality of terminals 104, the local data is accordingly sent to all the terminals 104 on which the transmission has been programmed for recording. In this situation, the division can be performed such that at least the central data stream for its part no longer delivers a decodable video signal (picture and sound). Only when both data sets (from the memory 110 of a terminal 104 and from the mass storage device 108) are combined can the transmission be played back in its entirety. The different possibilities for dividing the data into a central and a local portion have already been described in detail.

For playback purposes, the parts of the recording stored in the memory 110 of the selecting terminal 104 and the parts stored in the mass storage device 108 can be combined. To this end, the data stored in the terminal is first transferred to the PVR server, where it is combined. The complete video data is then sent to the terminal 104 as a realtime data stream for playback. This permits the construction of a particularly simple terminal 104 with minimal computing power. Since the data set stored in the terminal can be very small (several kilobytes per recording suffice in one embodiment of the invention), the user request to play back a specific transmission will only be insignificantly delayed, if at all, by the need to initially transfer data to the PVR server 102.

Alternatively, the parts of the recording stored in the memory 110 of the selecting terminal 104 and the parts stored in the mass storage device 108 can be combined in real time in the terminal 104. In response to a user input the incomplete video data is sent by means of the PVR server 102 from the mass storage device 108 as a near-realtime data stream to the terminal 104, where it is supplemented by the data stored in the terminal 104 and played back. In this situation, near-realtime data stream means that depending on the type of division of data selected between local memory 110 and mass storage device 108 it is also possible for larger data sets to be situated in the local memory, intro sequences for instance, which are first played back before the data which may have been buffered until then is prepared for playback from the mass storage device 108. The transfer of the data to the terminal should take place at least at the data rate with which the material was coded.

If intro sequences which also include header information, without which the remaining part of the recording stored in the mass storage device 108 is not useable, are stored in the memory 110 of the terminal 104 the playback can begin when requested by the user without delay caused by network operations because the intro can firstly be played back from the local memory while the remaining data is requested in the background from the mass storage device 108 and prepared for the playback. This accommodates the user expectation of being able to begin the playback without delay at the press of a button.

In addition to the options already mentioned for distributing the data to mass storage 108 and local memory 110, further options for distribution are immediately apparent to the person skilled in the art from the preceding detailed description of the invention. For example, it would be conceivable to logically form a type of wide RAID between hard disks of the mass storage 108 and the local hard disk 111 or the local flash memory 112. Such a configuration would also, given suitable definition of the RAID, have the effect of the content of the mass storage being useless without the local content.

Finally, it should be noted that the present invention can be used not only when—as described above—only one shared copy of a transmission is stored in the mass storage device 108 for all users but also in a situation when a separate copy of a transmission is stored in the mass storage device 108 for each user. In this case too it is possible and in some cases necessary to divide the stored transmissions into a part stored locally with regard to the user and a part stored centrally with regard to the service provider. 

1-16. (canceled)
 17. A configuration for storing and playing back TV transmissions, the configuration comprising: a PVR server for receiving a multiplicity of digitally coded TV channels, said PVR server having a device for recording TV transmissions to be stored; a mass storage device coupled to said PVR server for storing a main part of data to be stored; a multiplicity of terminals to be fed by said PVR server, at least one of said terminals selecting TV transmissions to be stored and transferring a selection to said PVR server, said selecting terminal having a memory receiving a small part of the data to be stored with regard to a recording; and a device for combining said part of said recording stored in said memory of said selecting terminal and said part of said recording stored in said mass storage device coupled to said PVR server, for playback by said selecting terminal.
 18. The configuration according to claim 17, wherein said device for recording TV transmissions to be stored causes said main part of said data to be stored in said mass storage device coupled to said PVR server to deliver decodable picture and sound information only when combined with said data stored in said memory of said selecting terminal.
 19. The configuration according to claim 17, wherein said memory of said selecting terminal is a flash memory or a mini hard drive.
 20. The configuration according to claim 17, wherein said device for recording TV transmissions to be stored causes header information for video data to be stored to be sent to said memory of said selecting terminal and remaining data to be stored, to be stored in said mass storage device coupled to said PVR server.
 21. The configuration according to claim 17, wherein said device for recording TV transmissions to be stored causes a time-limited starting sequence of video data to be stored to be sent to said memory of said selecting terminal and remaining data to be stored, to be stored in said mass storage device coupled to said PVR server.
 22. The configuration according to claim 17, wherein said device for recording TV transmissions to be stored causes every n^(th) data packet of video data to be stored to be sent to said memory of said selecting terminal and remaining data to be stored, to be stored in said mass storage device coupled to said PVR server.
 23. The configuration according to claim 17, wherein said PVR server combines said part of said recording stored in said memory of said selecting terminal and said part of said recording stored in said mass storage device coupled to said PVR server, and complete video data are sent to said terminal as a realtime data stream for playback.
 24. The configuration according to claim 17, wherein said terminal combines said part of said recording stored in said memory of said selecting terminal and said part of said recording stored in said mass storage device coupled to said PVR server in real time, and incomplete video data are sent from said mass storage device coupled to said PVR server as a near-realtime data stream to said terminal, where they are supplemented by said data stored in said memory of said terminal and played back.
 25. A method for storing and playing back TV transmissions, the method comprising the following steps: receiving a multiplicity of digitally coded TV channels at a PVR server feeding a multiplicity of terminals; selecting TV transmissions to be stored with a terminal and transferring the selection to the PVR server; recording TV transmissions to be stored, by sending a small part of the data to be stored with regard to the recording to a memory of the selecting terminal and storing a main part of the data to be stored in a mass storage device coupled to the PVR server; and combining the part of the recording stored in the memory of the selecting terminal and the part of the recording stored in the mass storage device coupled to the PVR server, with the selecting terminal for playback.
 26. The method according to claim 25, which further comprises delivering decodable picture and sound information from the main part of the data to be stored, which is stored in the mass storage device coupled to the PVR server, only when combined with the data stored in the memory of the selecting terminal.
 27. The method according to claim 25, wherein the memory of the selecting terminal is a flash memory or a mini hard drive.
 28. The method according to claim 25, which further comprises sending header information for video data to be stored to the memory of the selecting terminal, and storing remaining data to be stored in the mass storage device coupled to the PVR server.
 29. The method according to claim 25, which further comprises sending a time-limited starting sequence of video data to be stored to the memory of the selecting terminal, and storing the remaining data to be stored in the mass storage device coupled to the PVR server.
 30. The method according to claim 25, which further comprises sending every n^(th) data packet of video data to be stored to the memory of the selecting terminal, and storing remaining data to be stored in the mass storage device coupled to the PVR server.
 31. The method according to claim 25, which further comprises carrying out the step of combining the part of the recording stored in the memory of the selecting terminal and the part of the recording stored in the mass storage device coupled to the PVR server in the PVR server, and sending complete video data to the terminal as a realtime data stream for playback.
 32. The method according to claim 25, which further comprises carrying out the step of combining the part of the recording stored in the memory of the selecting terminal and the part of the recording stored in the mass storage device coupled to the PVR server in real time in the terminal, and sending incomplete video data from the mass storage device coupled to the PVR server as a near-realtime data stream to the terminal, where they are supplemented by the data stored in the memory of the terminal and played back. 